Method and device for generating waves in an aquarium

ABSTRACT

In order to generate waves in a volume of water of an aquarium, it is proposed that a storage container which extends beyond the surface of the volume of water should be provided in the aquarium. Using a pump, water is periodically pumped from the water container into the storage container and returned from the storage container into the aquarium. The energy delivered to the water during this leads to fluctuations in the position of the free surface of the volume of water and in-phase operation of the pump provides stronger surface displacements in the aquarium, which are comparable with a wave in open water and which expose the plants and living beings in the aquarium to an alternating mechanical load.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.11/125,652, filed May 10, 2005 the entire contents of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

The invention relates to a method for generating waves in an aquariumand to a device therefor.

The water in aquaria is normally circulated constantly through a filterfor cleaning purposes by using a pump. Although this does lead to flowsof water, they are negligibly small.

It is furthermore known to set up a stronger flow in such aquaria bymaking pumps extract water directly from the volume of water containedin the aquarium and return it directly into this volume of water.

For many applications, it is actually preferable to be able to replicatewaves in an aquarium. Waves are distinguished in that volumes of watermove to and fro periodically. These oscillating movements of the waterlead to corresponding alternating loads on plants and animals containedin the water.

SUMMARY OF THE INVENTION

In order to make these alternating loads available in an aquarium aswell, the present invention relates to a method and to a device forgenerating waves in the restricted space of an aquarium.

The invention makes use of the fact that water is a liquid which hasrelatively low internal friction. The energy needed in order to generatea wave process can therefore be introduced as small portions into thevolume of water, and the intended amplitude of the wave can be achievedby means of the total time duration of the energy input. This makes itpossible to deliver the kinetic and/or potential energy by usingstructures which have compact dimensions. This is preferable with a viewto the aquaria installed in living rooms, since extra equipment isperceived as aesthetically unpleasing there.

Preferred refinements of the invention are given in the dependentclaims.

One refinement of the invention is preferable with a view to setting upwaves as rapidly as possible with little energy input. The frequency atwhich the water level fluctuates in the aquarium in question ismeasured, and the energy delivery can then be synchronised accordingly.

One refinement is preferable with a view to generating stronger waves.

One method ensures that waves are not built up too strongly, and inparticular that water does not escape from the aquarium.

One refinement of the invention is also preferable with a view tominimal input of energy.

In the device, volumes of liquid are displaced while deliveringpotential optionally as well as kinetic energy, by raising a subvolumeof the water in the storage container to a level which is higher thanthe free level of the water in the aquarium. This volume can then bereturned into the aquarium under the effect of gravity, with kineticenergy optionally also being imparted to it by the delivery instrument.

As an alternative, a volume of water lying below the free level of thewater in the aquarium may be pumped and allowed to flow back afterswitching off the delivery instrument.

The delivery instrument may thus operate only intermittently and allowwater to flow back in the periods of time between the working cycles.The delivery instrument may also have a reversible direction ofrotation, however, and expel water from the storage container anddeliver it into the storage container in successive half-cycles. Withthis procedure, the kinetic energy necessary in order to set up strongerwaves is delivered to the water in a shorter time.

In both cases, it is favourable for the delivery instrument to have onlya small flow resistance.

A pump having a propeller which as a delivery element is distinguishedby a high throughput with a low pressure build-up. Such a pump can alsobe used equally well in both working directions.

The refined invention wherein the propeller which is enclosed by a pumphousing provided with through-openings in the circumferential wall andhas an axial delivery piece is preferable with a view to delivered waterflows which are as laminar as possible.

The refinement of the invention wherein the through-openings aredesigned as axial slots which are distributed in the circumferentialdirection and distributed equally is also used to avoid turbulence.

Another refinement of the invention has the advantage that the interiorof the storage container is substantially isolated from the volume ofwater in the aquarium.

Another refinement of the invention makes it possible to arrange thestorage container, and the delivery instrument belonging to it, close tothe normal surface of the aquarium so that a large part of the volume ofwater remains unperturbed.

A device wherein a level monitor is arranged at the upper end of thestorage container ensures that more water can be moved into the storagecontainer that is expedient in order to introduce potential energy.

The device can be constructed so that the delivery instrument isimmersed only very little into the volume of water in the aquarium,where it is visible.

The refinement of the invention ensures very effective transfer ofmotion energy to the water contained in the aquarium.

If the waves are generated by a device comprising a tilting bearingprovided for the aquarium and a drive engaged on the aquarium, thenvirtually all the interior of the aquarium can remain free of equipment.A device generally shown in FIG. 5 can also be retrofitted to aquariawhich are already being used.

A tilting bearing can be implemented without mechanical work on theaquarium.

A tipping drive is distinguished by very compact dimensions in thevertical direction. This drive can therefore be arranged at the bottomof the aquarium.

The two cooperating discs of the drive then form a compact unit withsmooth faces.

The effect achieved by one of the refinements of the invention is that,on the one hand, a friction lock is obtained between the working part ofthe tipping mechanism and the aquarium and, on the other hand, the driveconnection between the tipping drive and the aquarium permits smallertilting between the drive and the aquarium.

A tipping drive having a pressure actuator which is selectivelypressurized or relieved of pressure is distinguished by a particularlystraightforward and robust mechanical structure, and low productioncosts.

The refinement wherein the pressure actuator is a deformable monoblocelement is then preferable with a view to a further simplified structureand good reliability of the drive, with low costs.

The pressure actuator being enclosed by two telescopic parts ensuresthat the drive then has an attractive exterior and is protected againsttransverse loads.

Another refinement of the invention makes it possible to vary theintensity and shape of the waves generated in the aquarium in astraightforward way.

A controller is then distinguished by a straightforward structure. Thedelivery instrument or tilting drive is operated by a clock generator,the frequency of which is preferably adjustable, with a frequency atwhich the intended wave amplitude is obtained according to observationof the resulting waves.

In a device wherein the control end interacts with at least one leveldetector the program control can actually establish the oscillatingfrequency of the wave in the aquarium from the output signal of thelevel detector connected to it, and can tune it according to itsoperation.

Another refinement of the invention allows straightforward adaptation ofthe position of the level detector to the water level conditionsrespectively encountered in the aquarium.

Waves generated in the aquarium would also move to and fro the foodwhich is added to the aquarium at predetermined time intervals, and makeit settle on plants, stones etc. in the container. One effect achievedby a refinement of the invention is that the wave generation can besuspended for a predetermined length of time. This avoids theaforementioned loss of food.

For much aquarium stock, it is also preferable not to generate wavesduring the night.

One refinement of the invention makes it possible to adapt the wavegenerator in a very straightforward way to the respective filling levelof the aquarium. The wave generator should be arranged so that the onehand it can take in as much water as possible from the interior of theaquarium and, on the other hand, it is always immersed in the volume ofwater even with the strongest waves which are generated in the aquarium.

The effect achieved by one refinement of the invention is that an inlet,and outlet, a dirt extractor or the like essentially operate equallywhen there are waves and when the water is still.

Strong waves can be generated even in large aquaria.

The refinement of the invention wherein one of two wave generatorsoperates at different frequencies can then influence the waveform. Onthe one hand, particularly abrupt wave profiles can be generated bysuperposition of the long-wave and short-wave components; on the otherhand (with an appropriate amplitude and phase relation) it is alsopossible to set up short-wave flows of smaller amplitude.

Essentially periodic waves are then also obtained by a device whereinone of the two wave generators operates at twice the frequency of theother wave generator.

The refinements of the invention wherein the two wave generators lieclose together and their flow axes are aligned parallel or are arrangedon opposite walls with their flow axes pointing towards each other arepreferable with a view to generating large amplitudes by wave unitswhich reinforce one another.

Another refinement of the invention allows fine control over theamplitude of the waves being generated.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in more detail by exemplary embodimentswith reference to the drawings, in which:

FIG. 1 shows a vertical section through an aquarium having a wavegenerator;

FIG. 2 shows an axial view of a pump housing of a delivery pump, whichis part of the wave generator shown in FIG. 1;

FIG. 3 shows a block diagram of a controller for the wave generatorshown in FIG. 1;

FIG. 4 shows a similar representation to FIG. 1, but in which a modifiedwave generator is shown;

FIG. 5 shows a similar view to FIG. 1, but showing a wave generatorarranged outside the aquarium;

FIG. 6 shows a vertical section through a small-range linear drive,which may be used in the wave generator according to FIG. 5;

FIG. 7 shows a vertical section through a modified small-range linearactuator, which may also be used in the wave generator according to FIG.5;

FIG. 8 shows a similar view to FIG. 1, in which a further modified wavegenerator working inside the aquarium in shown;

FIG. 9 shows a view of an aquarium which is provided with two wavegenerators arranged on one of its narrow sides;

FIG. 10 shows a similar view to FIG. 9, but in which one wave generatoris arranged on each of the narrow sides of the aquarium; and

FIG. 11 shows a schematic side view of a wave generator and the way inwhich it is fastened to an aquarium wall.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIG. 1, the reference 10 denotes an aquarium in which there is avolume of water 12. Its free surface 14 is aligned horizontally in theabsence of any extraneous effects.

In order to set up conditions in the volume of water similar to thoseencountered when there are waves in open water, a wave generator denotedoverall by 16 is arranged in the aquarium 10 and periodically moves thesurface 14 of the volume of water 12 to and fro in oscillation duringoperation, between two extreme positions which are indicated at 18 and20 in the drawing, respectively by dashes and by dots and dashes.

The wave generators are generally arranged on a narrow side of theaquarium. There, they may also be placed in a corner where they do notimpede the view. The wave generators may, however, also be arranged inan end section of the aquarium which is covered on the outside by ashade.

It can be seen that there is a region in the middle of the aquariumwhere the water level changes little or not at all. In this region, asuction tube S via which a pump P takes in water near the surface dipsinto the upper layer of the volume of water. This water is sent by thepump P through a filter F and is fed back via a return line R into alower region of the volume of water in the aquarium 10.

The wave generator 16 comprises a storage container 22, which has acylindrical circumferential wall 24 and a bottom wall 26. A window 28,into which a delivery piece 30 of a delivery pump 32 is fittedessentially hermetically, is formed in the lower section of thecircumferential wall 24. The delivery piece 30 is carried by the endface of a pump housing 34, which has a multiplicity of slottedthrough-openings 36 distributed equally in the circumferential directionin its circumferential wall.

Inside the pump housing 34, there is a rotor denoted overall by 38 whichhas a hub 40 and propeller blades 42, distributed equally in thecircumferential direction, which are carried by the latter. The hub 40is linked in rotation with the shaft of a variable-direction electricmotor 44.

The electric motor 44 is supplied with energy, and has its direction ofrotation controlled, by a control unit 48 via a line 46.

As another input signal, the control unit 48 receives the actualposition of the surface 14, as measured at a point near the edge. Tothis end, a level sensor 50 which has a float 52 interacting with thesurface 14 is provided.

Another signal which the control unit 48 receives is the output signalof a level switch 54, which is fitted in the storage container 22 andresponds when the level inside the water container has reached apredetermined level 56.

Generally speaking, the control unit 48 operates so that it uses theoutput signal of the level sensor to determine which wave phase thesurface 14 is currently in. As a function of this phase, the controlunit 48 operates the delivery pump 32 so that potential or kineticenergy is delivered in-phase to the subvolume of water oscillatingintermediate storage container 22 and the volume of water 12.

Specifically, potential energy is delivered to the water when it israised by the delivery pump 32 to a level inside the storage container22 which is higher than the surface 14, and kinetic energy is deliveredto the water when it flows back from the upper region of the storagecontainer 22 into the interior of the aquarium 10, in which case thedelivery pump 32 may also be run in the opposite sense in which therotor 38 increases the flow rate of the water.

For lower energy input, however, the water may also be allowed to flowback from the storage container 22 merely under the effect of gravity.The delivery pump 32 designed as a propeller pump presents only a smallresistance to such a return flow.

Such a propeller delivery pump 32 for use in a seawater aquarium with avolume of about 400 to 2000 litres may typically have a delivery powerof between 2000 and 10000 litres per hour, with a delivery heightcorresponding to a water column of 20 to 30 cm.

If the water is intended to be further accelerated as it flows back, byoperating the delivery pump 32 in reverse, then a stabilizing cross 58as shown in FIG. 2 is preferably also provided in the delivery piece 30of the delivery pump 32. In this exemplary embodiment, it comprises fourthin plates lying in radial planes.

FIG. 3 shows a block diagram of the control unit 48.

The output of the level sensor 50 is connected to the input of anamplitude measuring loop 60. The latter contains an A/D converter and amemory, which is switched forward at a predetermined time interval andis dimensioned overall so that it can display one to three full periodsof the surface movement. The amplitude of the surface movement isdetermined from this and sent as a digital signal to a control computer62.

The output of the level sensor 50 is furthermore connected to a phaseand frequency measuring loop 64. This is constructed similarly as theamplitude measuring loop 60, in relation to digitising and storingmeasurement values, but the stored measurement data are with a view tothe period and the phase relation of the output signal of the levelsensor 50. The corresponding results are likewise sent to an input ofthe control computer 62.

This is also used to drive a voltage-controlled oscillator 66. Theoutput signal of the latter is sent to a controllable phase shifter 68.The control terminal thereof is connected to an output of the controlcomputer 70.

The output signal of the phase shifter 68 is sent to a pulse encoder 70which, generally speaking, operates so that it cuts a portion ofadjustable width from the half-wave of the output signal of the phaseshifter 68. This may, for example, be done by using a controllableamplitude discriminator. The pulse-width control terminal of the pulseencoder 70 is connected to another output of the control computer 62.

The control computer 62 furthermore interacts with a data memory 72 inwhich successive data triplets of amplitude, frequency and pulse widthare stored.

By using these stored data and the reported actual values of amplitudeand frequency, the control computer 62 then maximize the amplitude ofthe surface movement of the volume of water. This is done firstly byvarying the phrase relation (control signal for the phase shifter 68)and then by varying the activation time of the delivery pump 32 (controlsignal for the pulse encoder 70).

Another input of the control computer 72 is connected to an input unit74, which is shown as a keypad.

When a setpoint value entered here for the amplitude of the wave in theaquarium 10 is reached then the maximization of the wave amplitude isended, that is to say operation is thereafter continued with theequivalents for phase relation and pulse width unless a drop inamplitude necessitates readjustment of the phase relation and pulsewidth.

A last input of the control computer 62 is furthermore connected to theoutput signal of the level switch 54. When this responds, then thetrailing edge of a pulse generated by the pulse encoder 70 is alwaysgenerated, which avoids overfilling the storage container 22.

In the modified exemplary embodiment according to FIG. 4, componentswhich have been already explained above with reference to FIGS. 1 to 3are still provided with the same reference numbers. These componentswill not again be described in detail below.

A displacing plate 76, whose edge can be moved essentially fluid-tightlyin the manner of a piston inside the storage container 22, is arrangedinside the storage container 22 instead of the delivery pump 32. For thepurpose of the present application, it may be assumed that the storagecontainer 22 has a somewhat unrounded, for example elliptical crosssection so that the displacing plate 76 is guided securely againstrotation by the storage container 22.

The displacing plate 76 is carried by a threaded spindle 78, whichinteracts with a nut 80. The latter is held by an axial bearing (notshown) and is likewise driven by an electric motor 44 whose direction ofrotation is reversible. The electric motor 44 is driven similarly asdescribed above with reference to FIG. 3.

In the wave generator shown in FIG. 4, kinetic energy is thus deliveredto the volume of water in the aquarium 10 essentially by the downwardmovement of the displacing plate 76.

If no very great efforts are made with a view to the sealing between theedge of the displacing plate 76 and the inner surface of the storagecontainer 22, the displacing plate can be raised again with air flowinginto the space between the displacing plate and the water surface. Thewater then flows back under gravity through the window 28.

If there is a good seal between the displacing plate 76 and the storagecontainer 22, then water will be sucked from the aquarium into thestorage container 22 during the upward movement of the displacing plate76 so that kinetic energy is likewise delivered to the volume of waterduring the upward movement of the displacing plate 76.

The movement of the displacing plate 76 is matched by the control unit48 to the surging of the water in the aquarium 10, similarly asdescribed in the first exemplary embodiment in connection with theoperation of the delivery pump 32.

In the exemplary embodiment according to FIG. 5 as well, componentswhich have already been described above are provided with the samereference numbers. These components need not again be described indetail below.

In the exemplary embodiment according to FIG. 5, the wave generator 16is arranged outside the aquarium.

The aquarium 10 is arranged with its right-hand section in FIG. 5 on abearing rib 82, which is designed as a rail having a sector-shaped crosssection. This may extend over essentially the entire depth of theaquarium 10, and a central rail section may be milled.

A base 84, the length of which can be controlled, is provided in the endof the aquarium 10 placed on the left in FIG. 5.

As shown by FIGS. 5 and 6, the base 84 has a fixed lower base plate 86,which carries a central bearing pin 88.

A lower cam disc 90, which has a central bore 92 fitting the bearing pin88, is mounted so that that it can rotate on the latter. A lower endface of the cam disc 90 is flat and cooperates with the end wall of abearing chamber 91 which is formed in the base plate 86. An upper endface of the cam disc 90 is provided with a cam surface 93 which, forexample, may have a sinusoidal profile.

A complementary underlying cam surface 94 of an upper cam disc 96cooperates with the cam surface 93 of the lower cam disc 90. It also hasa central bore 98 which fits the bearing pin 88. An upper end face 100of the cam disc 96 is flat.

The end face 100 carries an elastic support 102 which fulfils twofunctions: on the one hand, it fixes the upper cam disc 96 securelyagainst rotation on the lower side of the aquarium 10 and, on the otherhand, it allows the lower side of the aquarium 10 to tilt on the base84.

The lower cam disc 90 is provided on its circumference with ring gear104 which engages with a pinion 106. The pinion 106 is mounted in apinion chamber 108 of the base plate 86 and is connected to the shaft ofthe electric motor 44.

An elastic support 110 provided on the lower side of the base plate 86provides secure and smooth placement of the base 94 on a support surface112.

FIG. 7 shows an alternative of a base 84 with a controllable height. Itcomprises two cooperating telescopic parts 114, 116, each of which is inthe form of a shallow cylindrical bowl. A diaphragm motor 118 made ofelastomeric material is fitted inside the space delimited by thetelescopic parts 114, 116.

The diaphragm motor 118 is connected to the output of a pressure pump120, which takes in from a storage container 122. The pressure pump 120is controlled similarly to the operation of the electric motor 44 in theexemplary embodiment according to FIG. 6.

The interior of the diaphragm motor 118 can furthermore be connected tothe storage container 122 by means of a solenoid valve 124. The solenoidvalve 124 is also controlled by the control unit 48 (generally speakingby the negative half-wave of the output signal of the phase shifter 68).

The pressurization and pressure release of the diaphragm motor 118 arecontrolled so that energy is delivered to the water in the aquarium in acorrect phase relation with the surging of the water in the aquarium.

The exemplary embodiment according to FIG. 7 also differs from the onein FIG. 6 in that the upper end face of the base 84 (the upper-lyingbottom of the upper telescopic part 114) is in the shape of a cap, asshown at 126. The support 102 may therefore be obviated.

In the exemplary embodiment according to FIG. 8 as well, componentswhich have been already described are still provided with the samereference numbers.

Inside the aquarium 10, there is a vertical displacing plate 128 whichhas a sleeve 130 at the upper end which extends over a guide rod 132carried by the upper edge of the aquarium.

The displacing plate 128 furthermore carries a nut 134, the axis ofwhich is parallel to the axis of the sleeve 130. The nut 134 interactswith a threaded spindle 136 which is in turn driven via toothed wheels137, 139 by an electric motor 44, which is likewise fixed to the upperedge of the aquarium 10.

The electric motor 44 is driven similarly to the electric motor workingon the horizontal displacing plate 76 in FIG. 4.

Wave-like displacements of the surface 14 of the volume of water 12 areagain obtained by movement of the displacing plate 128.

In the aquarium 10 shown in FIG. 9, two wave generators 16-1 and 16-2are placed on the right-hand narrow wall. Their delivery pieces 30 arealigned parallel.

The wave generators 16-1 and 16-2 are connected to supply terminals “1”and “2” of the control unit 48. The latter has a knob “I” on a consolefor each of the two wave generators 16-1 and 16-2, by which theintensity of the water flow delivered by the wave generator can beadjusted, and a knob “P” by which the phase relation of a packet ofwater delivered by the wave generator can be adjusted.

The control unit 48 furthermore has other output terminals “−1” and“−2”, not required in the exemplary embodiment according to FIG. 9, atwhich the inverted output signals of the terminals “1” and “2” areprovided.

The control unit shown in FIG. 9 operates generally speaking so that itmakes the two wave generators 16-1 and 16-2 deliver packets of water andtake water back into their storage containers essentially synchronously.The water flows generated by the wave generators 16-1 and 16-2 aretherefore added together. Waves with a large amplitude can thus begenerated in long aquaria 10 by the arrangement shown in FIG. 9.

The different adjustability of the intensity and phase relation of thewater flows delivered by the wave generators 16-1 and 16-2 can be usedto compensate for differences in the propagation behaviour for thesewater flows, which are due to different contouring and different flowresistances of the content of the aquarium (sand piles, plants etc.).

The oscillation frequency of the volume of water contained in them, andthe maximum achievable or recommendable wave height will be compiledbelow for some aquaria.

 1.  2. Dimensions (L × B × H)  3. Frequency  4. Max wave height  5.  6. 7.  8. 70 × 50 × 50 cm  9. 0.45 s 10. 40 mm 11. 100 × 70 × 60 cm 12.0.56 s 13. 35 mm 14. 120 × 70 × 60 cm 15. 0.63 s 16. 35 mm 17. 150 × 100× 60 cm 18. 0.83 s 19. 30 mm 20. 180 × 100 × 60 cm 21. 0.86 s 22. 30 mm23. 220 × 80 × 50 cm 24. 1.10 s 25. 25 mm 26. 200 × 80 × 65 cm 27. 1.15s 28. 25 mm

Wave formation by superposition is particularly preferable for aquariawith a length of more than two metres. Besides the aforementionedfundamental oscillation, the half-period is also used. One generator isthus operated with a frequency which is about 1.1 s for a 2 m aquarium,and a second wave generator is operated with a frequency of about 0.55s, i.e. twice the frequency.

The superposition of waves with a different wavelength also makes itpossible to influence the waveform. It is thus possible to generateparticularly strong waves, raise waves with steep fronts or evengenerate waves which are distributed in the form of fine ripples overthe surface.

In order to switch off the wave generation during the night, the controlunit 48 may interact with a sensor 148 responsive to ambient light orthe aquarium illumination. When this establishes that the illuminationhas fallen below a predetermined level, it makes the control unit 48suppress the output of activation signals to the wave generator/wavegenerators.

As an alternative, it is also possible for the amplitude of the waveproduced at night merely to be reduced on the basis of the output signalof the sensor 148.

When light strikes the sensor 148 again, whether daylight or light fromthe aquarium illumination, then the wave generator 16 is turned onagain.

The control unit 48 furthermore has a button 150 which is pressed whenfish in the aquarium need to be fed. The button 150 activates a timer(not shown in detail) in the control unit 48 which suppresses the wavegeneration for a predetermined length of time, which may be about 10minutes in practice. In this way, food scattered over the surface of thewater remains close to where it was scattered, and is not washed intowater plants or decorative objects.

After the length of time specified by the timer has elapsed, the wavegenerator is automatically turned on again.

If desired, the output terminals “−1” and “−2” providing the invertedsignals on the control unit 48 may be omitted, and the inverted signalsmay be applied if required by using jumpers on the normal outputterminals.

An amplified flow of water is obtained in the exemplary embodimentaccording to FIG. 10. Now, however, the two wave generators 16-1 and16-2 are arranged on the two mutually opposite narrow sides of theaquarium. The two delivery pieces 30 of the wave generators now facetowards each other. In order to obtain a flow amplification with thisgeometry, the wave generator 16-2 is now connected to the outputterminal “−2” of the control unit 48.

FIG. 11 shows the way in which a wave generator 16 is fitted to the wallof an aquarium 10. A guide rail 138 is fastened to the upper end of theaquarium wall using a screw clamp 140. A support slide 142 runs in theguide rail 138. It can be fixed using a clamp screw 144 once it is inthe correct position.

of the wave generator 16 is supported on the inside of the aquarium wallby an elastomeric support part 146, which has a similar geometry to asucker.

The height of the wave generator 16 can in this way be adjusted, and itcan be secured to the aquarium while being exactly parallel to the wallof the aquarium.

The immersion depth of the wave generator 16 is adjusted so that, on theone hand, no water reaches the lid of the storage container and, on theother hand, the delivery pump 32 never emerges from the water, whichwould produce undesirable noise.

The control unit 48 may itself also be secured to the wall of theaquarium 10. This may be done, for example, by using self-adhesiveplastic hook strips.

With the wave generators as described above, in aquaria which maytypically have a volume of from 200 to 1200 litres, it is possible togenerate waves and water movements which are very similar to thatencountered in reef biotopes. Since an oscillating movement is impartedto the volume of water in the aquarium, it is possible to set up evenhigh waves with little energy input.

If a wave generator 16 is provided with a large storage container 22, itis also possible to simulate an ebb and flow by keeping water pumped outfor longer times. In such a case, the delivery pieces 30 of the deliverypump 32 will preferably be provided with a large-area plate-magnetvalve, by which the water pumped from the interior of the aquarium 10into the storage container 20 can be held there for a longer length oftime, even if the delivery pump 32 is then turned off.

1. A device for generating waves in a volume of water which is held inan aquarium defining a water surface, comprising: a) means forintermittent delivering at least one of potential and kinetic energy tothe volume of water including a delivery instrument and a variabledirection electric motor; b) a control unit for controlling delivery ofthe at least one of potential and kinetic energy to the volume of water,wherein the control unit is operable to adjust a frequency of theintermittent delivery of the at least one of potential and kineticenergy into the aquarium volume of water; and c) at least one waterlevel detector in electronic communication with the control unit, thecontrol unit interacting with the at least one water level detector todetermine which wave phase the water surface is currently in andcontrols the direction of the electric motor in accordance with the wavephase determined.
 2. Device according to claim 1 wherein the controlunit comprises a clock generator having an adjustable period.
 3. Deviceaccording to claim 1 wherein at least one of the level detectors can befitted to the aquarium at a selectable height.
 4. Device according toclaim 1 further comprising a clock generator of the control unit, withwhich the delivery can be stopped for a predetermined length of time. 5.Device according to claim 1, further comprising a stopping instrumentfor stopping the delivery instrument, the stopping instrument having atime switch clock or a sensor which responds when the strength of theambient light falls below a predeterminable value.
 6. A device accordingto claim 1, wherein the means for delivering at least one of potentialand kinetic energy to the volume of water comprises a pump displacingwater in at least one of a substantially vertical or a substantiallyhorizontal direction.
 7. The device of claim 6, wherein the pumpcomprises: a displacement plate having opposed edges, the displacementplate selectively moveable in the volume of water.
 8. The device ofclaim 7, wherein the opposed edges of the displacement plate arepositioned and adapted to be spaced from aquarium walls defining thevolume of water held by the aquarium.
 9. The device of claim 7 furthercomprising a storage container adapted to be at least partiallypositioned in the aquarium volume of water, the storage container havingat least two walls defining a subvolume of water, wherein thedisplacement plate is positioned between the at least two storagecontainer walls and the plate opposing edges are spaced from the atleast two storage container walls.
 10. The device of claim 1 wherein thedelivery instrument further comprises: an elongate thin plate extendingdownward into the volume of water transverse to the water surface; aspindle rod at least partially positioned between the motor and theplate, the spindle rod having a threaded portion threadibly engaging aportion of the plate, the spindle rod connected to the motor distantfrom the plate; and a guide rod positioned substantially parallel to thespindle rod and moveably connected to the plate, wherein the water leveldetector generates an output signal to the motor to synchronize rotationof the motor and translation of the plate in a direction parallel to thewater surface according to the detected wave phase by the water leveldetector.